Temporary pacing is used as an emergency treatment for atrioventricular block of the heart or right bundle branch block caused by serious arrhythmia, myocardial infraction or the like. By the term "temporary pacing" used herein is meant pacing not using a pacemaker implanted in a body. Namely, in temporary pacing, only a pacing electrode is inserted into a body, and the proximal end of an electrode catheter is located outside the body of a patient. Connection between wire connected to the electrode and a pacemaker is performed outside the body of the patient and the pacemaker is generally set outside the body.
In contrast, in implanted pacing, a connecting portion between an implantable type pacemaker and an implantable type pacemaker lead is embedded in the body, and further, the pacemaker is generally implanted in the body of a patient.
When the catheter for temporary pacing is applied, for example, a peripheral vein such as the femoral vein or subclavian vein is punctured by a catheter introducer through an incised portion of the skin. The catheter for temporary pacing is inserted through this introducer and the distal end of the catheter is held on the apex of the right ventricle, and positive and negative leads at the proximal end of the catheter are connected to terminals of the temporary pacemaker and a switch is turned on to start the pacemaker and initiate pacing. The stimulation rate, the stimulation output amplitude and the electrocardiographic sensitivity are adjusted to desired levels and the catheter-inserted portion of the skin is sutured.
Current temporary pacemakers are generally of the "demand" type, and in a pacemaker of this type, for example, the stimulation rate can be analogically adjusted to a desired level (for example, 30 to 150 pulses per minute) and similarly, the stimulation output amplitude can be analogically adjusted to a desired level (for example, 0.1 to 15 V). Moreover, the pacemaker has a mechanism for manually adjusting the electrocardiographic sensitivity to a desired level (for example, 0.5 to 20 mV). At least three variable resistors should be built into the pacemaker for performing these analogical adjustments. The abovementioned three adjustment mechanisms should be disposed, although temporary pacemakers comprising still another mechanism capable of the analogical adjustment have been proposed. Each of these variable resistors should be strong and durable enough that it can be used repeatedly, and the mechanical shaft of the variable resistor should have a water-proof and sterilizable structure. These variable resistors generally have a round shape having a diameter of about 19 mm and a thickness of about 20 mm. Accordingly, the pacemakers come in a large size such that the length is about 15 cm, the width is 10 cm, and the height is about 3 cm and it is difficult to fix them to the body surface of a patient. Therefore, the pacemakers must be arranged apart from the body surface portion, and thus handling is difficult and complicated. Moreover, at the transfer of a patient, often the catheter is pulled by the temporary pacemaker and the catheter is pulled out.
Another important problem resides in the connection of the catheter for temporary pacing to the temporary pacemaker. To prevent infection, the hands and fingers of an operator inserting the catheter must be carefully disinfected prior to the operation of the catheter. To confirm that pacing will be carried out smoothly, the catheter is connected to the temporary pacemaker after the insertion of the catheter, and a test working is conducted. Since the temporary pacemaker has a structure in which sterilization is impossible or the temporary pacemaker is so large and heavy that it cannot be sterilized, the temporary pacemaker is used in the non-sterilized condition. Moreover, when pacing is not smoothly carried out, often the operator handles the catheter again, but the operator is not allowed to touch the unclean temporary pacemaker. In general, another operator adjusts at least three variable resistors as mentioned above according to the condition of a patient. But, in an emergency, for example, during the night, it is often difficult to obtain two operators, and this situation is a serious problem for a life-saving emergency treatment fighting the clock.
For insertion and indwelling to the intended part, a heavy metal compound or a radiopaque medium are incorporated into the body tube of the catheter for temporary pacing and the operation is carried out under fluoroscopic observation. Alternatively, a pressure-measuring apparatus is connected to the lumen of the catheter, communicating with the distal end opening, on the side of the proximal end of the catheter, and the catheter is inserted and held while measuring the pressure at the distal end of the catheter. Furthermore, there is already known a catheter for temporary pacing, which is constructed by attaching a balloon to the top end of a catheter as mentioned above so that the catheter can float and flow in the heart and blood vessels.
In the above-mentioned conventional catheter for temporary pacing, the distal end electrode is formed from a hard metal such as stainless steel or platinum, and even in the balloon catheter for temporary pacing, the distal end electrode projects over the balloon when the balloon is inflated. Accordingly, where the conventional pacing catheter is inserted into the intended part through the skin and held on this part, the heart and blood vessels are often damaged by the distal end electrode, and if the catheter is forcibly proceeded, there is a risk of perforation.
The inventors carried out investigations into ways of solving the foregoing problems, and noted that if the size of the temporary pacemaker function is diminished and this function is embedded in the pacing catheter, the pacemaker function can be used in the state attached to the body of a patient and handling inconvenience is eliminated. It also was noted that, if a catheter having a temporary pacing function therein is packaged in the sterilized condition, a second operator required for connecting the temporary pacemaker to the pacing catheter becomes unnecessary. The inventors further investigated the possibility of integration and sterilization.
Moreover, the inventors investigated ways in which a catheter for temporary pacing comprising a balloon attached to the vicinity of the distal end is developed, in which the distal end electrode is not projected over the balloon when the balloon is inflated, and as a result, the present invention was completed.